With increasing customer demand for transmitting and receiving increasingly greater amounts of information, telecommunication and cable companies are being pushed to upgrade their communication network infrastructures. In order to supply more information in the form of video, audio and telephony at higher rates, higher bandwidth communication network upgrades are required. Twisted copper wire does not support high bandwidths over a great distance and while coax cable does a better job, it too has reach and bandwidth limitations. Optical fiber can provide virtually unlimited bandwidth thus enabling broadband and multimedia services.
Modern telephone communication network infrastructures, such as fiber in the loop networks (FITL), utilize a combination of fiber optics and twisted pair wire to send communications data to a customer. While modern cable communication network infrastructures, such as Hybrid Fiber Coax networks (HFC), utilize a combination of fiber optics and coax cable to send communication data to a customer. Generally, customers are served by the twisted pair wire or coax cable in the last mile of the telecommunication networks or within the last two to three miles of cable networks. In order to achieve high bandwidths at a customer location, the fiber optic loop must be brought closer to the customer so that the copper drop is of a sufficiently short distance and will be capable of supporting higher data transfer rates.
One major problem with bringing fiber cable within a short distance of a customer location is the added burden of maintaining the multitude of optical to copper drop sites. These drop sites are network elements that are called optical network units (ONUs) or optical network terminals (ONTs) in telecommunication networks and optical node (or simply a node) in cable networks and generally serve to convert signals between the optical domain of a fiber and electrical domain of a twisted copper wire or coax cable.
A significant part of the maintenance of these drop sites is supplying their power requirements. Optical fiber itself is not capable of carrying the electricity to power these drop sites. This creates a challenge in planning, distributing and deployment of electricity to power the drop sites' energy needs. Furthermore, reserve power must also be provided if the main power to the drop site fails with enough reserve capacity capable of meeting performance and reliability requirements of the network. This is often the case with Lifeline telephony service, which is required on telecommunication networks. Lifeline telephone means that the customer telephones must remain energized and operational during an AC power interruption or outage.
The subscriber gateway or customer premise equipment (CPE) found at the terminal end of the telecommunication and cable networks are assumed to be provided with power and reserve power from the subscriber or customer premise. The drop sites can be centrally powered from a distributed copper facility or a power node located near a cluster of drop sites, or locally powered from a nearby commercial power source, or with solar photovoltaic energy.
In the case of centralized power, power can be provided over new or existing copper facilities. Power can also be provided on separate twisted pair wire or coax cable that are bonded to the outside of a fiber or deployed with the fiber during installation of the fiber. However, centralized power is a strategy that requires a separate power network to be deployed that is separate from the information network. With increasing distances between a central office (CO) or head end to the remote drop sites increased voltages are required on the power network to feed the drop site energy needs. However, increased voltages raise craft safety issues. The power network may be augmented with power nodes located near a cluster of drop sites, however additional metallic enclosures increase susceptibility to electrical surges caused by lightning and power-line induction. Furthermore, there is the 24-hour a day cost of supplying electricity to the power network, as well as regular maintenance and support of the power network itself including regular replacement of batteries for Lifeline services, which are generally located at the CO or head end.
In the case of locally powered drop sites, power is derived near a drop site and reserve power is provided with batteries at the drop site. The primary energy source for this architecture is commercial AC power tapped from a power utility's facility. The power supply is placed in a small environmentally hardened enclosure that could be co-located with a drop site; however, the batteries are generally in the same enclosure as the drop site. This results in a large number of battery sites and power access points. Generally the cost of this type of system is high primarily due to the cost of connecting drop sites to a commercial power source. Regional power utility companies may insist on metered connections to their power grid, incurring a one-time ac meter installation and connection charge to be levied. Additionally a minimum monthly meter charge may be levied regardless of usage. This poses a major problem when the monthly energy consumption of a drop site is significantly lower than the minimum charge.
In the case of powering the communication network infrastructure with solar power, this strategy minimizes some of the disadvantages of centralized and locally powering such as vulnerability to lightning and limited battery reserve, allowing fiber to be the sole distribution facility. Solar panels and large batteries are co-located at drop sites, which power the drop sites continuously without any connection to any power gird. However, its use is limited to areas with direct access to sunlight as the output of solar panels decreases with a reduction in incident solar energy. Therefore, this strategy cannot be used everywhere. In addition, solar power requires the highest amount of battery capacity (Wh) to be installed.
As such, a need exists for a system and method for powering a fiber optic communication network that brings fiber within a short distance of a subscriber or customer location. The power strategy or architecture of the fiber optic communication network must be capable of supporting and operating the multitude of drop sites in a cost effective and maintainable manner.